This invention relates to electrochemical cells and particularly to methods for filling such cells with electrolytes. Still more particularly, the invention relates to methods of filling lithium containing cells with volatile thionyl chloride.
Such cells are known in the art and comprise a metal can and cover having a terminal insulatingly mounted therethrough. The anode material is usually lithium or one of the alkali metals and the cathode can be carbon. The electrolyte can be primarily thionyl chloride containing a solute of lithium-aluminum tetrachloride.
Great care is required in assembling these cells because of the reactivity of the components, particularly the lithium and the thyionyl chloride.
It has been suggested in the past to fill the cells under vacuum conditions; that is, the metal can and cover are partially sealed, leaving a small opening as a fill port. The cells were placed in a vacuum chamber and a high vacuum drawn thereon, this vacuum being below the boiling point of the electrolyte. Electrolyte was then introduced into the chamber in an amount to cover the cell, and then the chamber was returned to atmospheric pressure. Excess electrolyte was then sucked from the chamber into a reservoir and the cells removed.
This procedure lacked consistency and frequently damaged the cells. Often, the cover and terminal contained therein were covered by the electrolyte. Further, the electrolyte was introduced into the chamber under a high vacuum (30" Hg) causing the electrolyte to boil and spatter the cells.